Electronic States and Geometrical Structures of Hubbard Clusters

Abstract

The 4-site Hubbard clusters with several geometrical structures are investigated. The stable structures are found to be the close packed, distorted and loose packed structures for the less than half-filled, nearly half-filled and more than half-filled cases, respectively. The distorted structure which is due to the Jahn-Teller instability shows a characteristic non-uniform charge distribution. The electron correlation has remarkable effects on the stability of the distorted structure with the non-uniform charge distribution and the appearance of a high spin configuration. The structural distortion due to the Jahn-Teller effect is discussed in relation to the charge density wave in low-dimensional solids.